1
|
Fuller KB, Requijo RM, Schneider DA, Lucius AL. NTPs compete in the active site of RNA polymerases I and II. Biophys Chem 2024; 314:107302. [PMID: 39180852 PMCID: PMC11401760 DOI: 10.1016/j.bpc.2024.107302] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 07/19/2024] [Accepted: 07/22/2024] [Indexed: 08/27/2024]
Abstract
Eukaryotes express at least three RNA polymerases (Pols) carry out transcription, while bacteria and archaea use only one. Using transient state kinetics, we have extensively examined and compared the kinetics of both single and multi-nucleotide additions catalyzed by the three Pols. In single nucleotide addition experiments we have observed unexpected extension products beyond one incorporation, which can be attributed to misincorporation, the presence of nearly undetectable amounts of contaminating NTPs, or a mixture of the two. Here we report the development and validation of an analysis strategy to account for the presence of unexpected extension products, when they occur. Using this approach, we uncovered evidence showing that non-cognate nucleotide, thermodynamically, competes with cognate nucleotide for the active site within the elongation complex of Pol I, ΔA12 Pol I, and Pol II. This observation is unexpected because base pairing interactions provide favorable energetics for selectivity and competitive binding indicates that the affinities of cognate and non-cognate nucleotides are within an order of magnitude. Thus, we show that application of our approach will allow for the extraction of additional information that reports on the energetics of nucleotide entry and selectivity.
Collapse
Affiliation(s)
- Kaila B Fuller
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ryan M Requijo
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, AL 35294, USA.
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
2
|
Fuller KB, Jacobs RQ, Carter ZI, Cuny ZG, Schneider DA, Lucius AL. Global kinetic mechanism describing single nucleotide incorporation for RNA polymerase I reveals fast UMP incorporation. Biophys Chem 2024; 312:107281. [PMID: 38889653 PMCID: PMC11260521 DOI: 10.1016/j.bpc.2024.107281] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2024] [Revised: 05/22/2024] [Accepted: 06/06/2024] [Indexed: 06/20/2024]
Abstract
RNA polymerase I (Pol I) is responsible for synthesizing ribosomal RNA, which is the rate limiting step in ribosome biogenesis. We have reported wide variability in the magnitude of the rate constants defining the rate limiting step in sequential nucleotide additions catalyzed by Pol I. in this study we sought to determine if base identity impacts the rate limiting step of nucleotide addition catalyzed by Pol I. To this end, we report a transient state kinetic interrogation of AMP, CMP, GMP, and UMP incorporations catalyzed by Pol I. We found that Pol I uses one kinetic mechanism to incorporate all nucleotides. However, we found that UMP incorporation is faster than AMP, CMP, and GMP additions. Further, we found that endonucleolytic removal of a dimer from the 3' end was fastest when the 3' terminal base is a UMP. It has been previously shown that both downstream and upstream template sequence identity impacts the kinetics of nucleotide addition. The results reported here show that the incoming base identity also impacts the magnitude of the observed rate limiting step.
Collapse
Affiliation(s)
- Kaila B Fuller
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ruth Q Jacobs
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, AL 35294, USA
| | | | - Zachary G Cuny
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, AL 35294, USA.
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
3
|
Fuller KB, Jacobs RQ, Schneider DA, Lucius AL. Reversible Kinetics in Multi-nucleotide Addition Catalyzed by S. cerevisiae RNA polymerase II Reveal Slow Pyrophosphate Release. J Mol Biol 2024; 436:168606. [PMID: 38729258 PMCID: PMC11162919 DOI: 10.1016/j.jmb.2024.168606] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2024] [Revised: 05/01/2024] [Accepted: 05/05/2024] [Indexed: 05/12/2024]
Abstract
Eukaryotes express at least three nuclear DNA dependent RNA polymerases (Pols). Pols I, II, and III synthesize ribosomal (r) RNA, messenger (m) RNA, and transfer (t) RNA, respectively. Pol I and Pol III have intrinsic nuclease activity conferred by the A12.2 and C11 subunits, respectively. In contrast, Pol II requires the transcription factor (TF) IIS to confer robust nuclease activity. We recently reported that in the absence of the A12.2 subunit Pol I reverses bond formation by pyrophosphorolysis in the absence of added PPi, indicating slow PPi release. Thus, we hypothesized that Pol II, naturally lacking TFIIS, would reverse bond formation through pyrophosphorolysis. Here we report the results of transient-state kinetic experiments to examine the addition of nine nucleotides to a growing RNA chain catalyzed by Pol II. Our results indicate that Pol II reverses bond formation by pyrophosphorolysis in the absence of added PPi. We propose that, in the absence of endonuclease activity, this bond reversal may represent kinetic proofreading. Thus, given the hypothesis that Pol I evolved from Pol II through the incorporation of general transcription factors, pyrophosphorolysis may represent a more ancient form of proofreading that has been evolutionarily replaced with nuclease activity.
Collapse
Affiliation(s)
- Kaila B Fuller
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ruth Q Jacobs
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
4
|
Jacobs RQ, Schneider DA. Transcription elongation mechanisms of RNA polymerases I, II, and III and their therapeutic implications. J Biol Chem 2024; 300:105737. [PMID: 38336292 PMCID: PMC10907179 DOI: 10.1016/j.jbc.2024.105737] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2023] [Revised: 01/30/2024] [Accepted: 02/01/2024] [Indexed: 02/12/2024] Open
Abstract
Transcription is a tightly regulated, complex, and essential cellular process in all living organisms. Transcription is comprised of three steps, transcription initiation, elongation, and termination. The distinct transcription initiation and termination mechanisms of eukaryotic RNA polymerases I, II, and III (Pols I, II, and III) have long been appreciated. Recent methodological advances have empowered high-resolution investigations of the Pols' transcription elongation mechanisms. Here, we review the kinetic similarities and differences in the individual steps of Pol I-, II-, and III-catalyzed transcription elongation, including NTP binding, bond formation, pyrophosphate release, and translocation. This review serves as an important summation of Saccharomyces cerevisiae (yeast) Pol I, II, and III kinetic investigations which reveal that transcription elongation by the Pols is governed by distinct mechanisms. Further, these studies illustrate how basic, biochemical investigations of the Pols can empower the development of chemotherapeutic compounds.
Collapse
Affiliation(s)
- Ruth Q Jacobs
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, Alabama, USA.
| |
Collapse
|
5
|
Cooper SL, Lucius AL, Schneider DA. Quantifying the impact of initial RNA primer length on nucleotide addition by RNA polymerase I. Biophys Chem 2024; 305:107151. [PMID: 38088007 DOI: 10.1016/j.bpc.2023.107151] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Revised: 11/30/2023] [Accepted: 12/04/2023] [Indexed: 01/03/2024]
Abstract
Transient state kinetic studies of eukaryotic DNA-dependent RNA polymerases (Pols) in vitro provide quantitative characterization of enzyme activity at the level of individual nucleotide addition events. Previous work revealed heterogeneity in the rate constants governing nucleotide addition by yeast RNA polymerase I (Pol I) for each position on a template DNA. In contrast, the rate constants that described nucleotide addition by yeast RNA polymerase II (Pol II) were more homogeneous. This observation led to the question, what drives the variability of rate constants governing RNA synthesis by Pol I? Are the kinetics of nucleotide addition dictated by the position of the nascent RNA within the polymerase or by the identity of the next encoded nucleotide? In this study, we examine the impact of nucleotide position (i.e. nascent RNA primer length) on the rate constants governing nine sequential nucleotide addition events catalyzed by Pol I. The results reveal a conserved trend in the observed rate constants at each position for all primer lengths used, and highlight that the 9-nucleotide, or 9-mer, RNA primer provides the fastest observed rate constants. These findings suggest that the observed heterogeneity of rate constants for RNA synthesis by Pol I in vitro is driven primarily by the template sequence.
Collapse
Affiliation(s)
- Stephanie L Cooper
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, Heersink School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
6
|
Fuller KB, Jacobs RQ, Schneider DA, Lucius AL. The A12.2 Subunit Plays an Integral Role in Pyrophosphate Release of RNA Polymerase I. J Mol Biol 2023; 435:168186. [PMID: 37355033 PMCID: PMC10529642 DOI: 10.1016/j.jmb.2023.168186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2023] [Revised: 06/13/2023] [Accepted: 06/17/2023] [Indexed: 06/26/2023]
Abstract
RNA polymerase I (Pol I) synthesizes ribosomal RNA (rRNA), which is the first and rate-limiting step in ribosome biosynthesis. A12.2 (A12) is a critical subunit of Pol I that is responsible for activating Pol I's exonuclease activity. We previously reported a kinetic mechanism for single-nucleotide incorporation catalyzed by Pol I lacking the A12 subunit (ΔA12 Pol I) purified from S. cerevisae and revealed that ΔA12 Pol I exhibited much slower incorporation compared to Pol I. However, it is unknown if A12 influences each nucleotide incorporation in the context of transcription elongation. Here, we show that A12 contributes to every repeating cycle of nucleotide addition and that deletion of A12 results in an entirely different kinetic mechanism compared to WT Pol I. We found that instead of one irreversible step between each nucleotide addition cycle, as reported for wild type (WT) Pol I, the ΔA12 variant requires one reversible step to describe each nucleotide addition. Reversibility fundamentally requires slow PPi release. Consistently, we show that Pol I is more pyrophosphate (PPi) concentration dependent than ΔA12 Pol I. This observation supports the model that PPi is retained in the active site of ΔA12 Pol I longer than WT Pol I. These results suggest that A12 promotes PPi release, revealing a larger role for the A12.2 subunit in the nucleotide addition cycle beyond merely activating exonuclease activity.
Collapse
Affiliation(s)
- Kaila B Fuller
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Ruth Q Jacobs
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA.
| |
Collapse
|
7
|
Carter ZI, Jacobs RQ, Schneider DA, Lucius AL. Transient-State Kinetic Analysis of the RNA Polymerase II Nucleotide Incorporation Mechanism. Biochemistry 2023; 62:95-108. [PMID: 36525636 PMCID: PMC10069233 DOI: 10.1021/acs.biochem.2c00608] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Eukaryotic RNA polymerase II (Pol II) is an essential enzyme that lies at the core of eukaryotic biology. Due to its pivotal role in gene expression, Pol II has been subjected to a substantial number of investigations. We aim to further our understanding of Pol II nucleotide incorporation by utilizing transient-state kinetic techniques to examine Pol II single nucleotide addition on the millisecond time scale. We analyzed Saccharomyces cerevisiae Pol II incorporation of ATP or an ATP analog, Sp-ATP-α-S. Here we have measured the rate constants governing individual steps of the Pol II transcription cycle in the presence of ATP or Sp-ATP-α-S. These results suggest that Pol II catalyzes nucleotide incorporation by binding the next cognate nucleotide and immediately catalyzes bond formation and bond formation is either followed by a conformational change or pyrophosphate release. By comparing our previously published RNA polymerase I (Pol I) and Pol I lacking the A12 subunit (Pol I ΔA12) results that we collected under the same conditions with the identical technique, we show that Pol II and Pol I ΔA12 exhibit similar nucleotide addition mechanisms. This observation indicates that removal of the A12 subunit from Pol I results in a Pol II like enzyme. Taken together, these data further our collective understanding of Pol II's nucleotide incorporation mechanism and the evolutionary divergence of RNA polymerases across the three domains of life.
Collapse
Affiliation(s)
- Zachariah I Carter
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama35233, United States
| | - Ruth Q Jacobs
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama35233, United States
| | - David A Schneider
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, Alabama35233, United States
| | - Aaron L Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, Alabama35233, United States
| |
Collapse
|
8
|
Jacobs RQ, Carter ZI, Lucius AL, Schneider DA. Uncovering the mechanisms of transcription elongation by eukaryotic RNA polymerases I, II, and III. iScience 2022; 25:105306. [PMID: 36304104 PMCID: PMC9593817 DOI: 10.1016/j.isci.2022.105306] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Revised: 08/16/2022] [Accepted: 10/03/2022] [Indexed: 11/01/2022] Open
Abstract
Eukaryotes express three nuclear RNA polymerases (Pols I, II, and III) that are essential for cell survival. Despite extensive investigation of the three Pols, significant knowledge gaps regarding their biochemical properties remain because each Pol has been evaluated independently under disparate experimental conditions and methodologies. To advance our understanding of the Pols, we employed identical in vitro transcription assays for direct comparison of their elongation rates, elongation complex (EC) stabilities, and fidelities. Pol I is the fastest, most likely to misincorporate, forms the least stable EC, and is most sensitive to alterations in reaction buffers. Pol II is the slowest of the Pols, forms the most stable EC, and negligibly misincorporated an incorrect nucleotide. The enzymatic properties of Pol III were intermediate between Pols I and II in all assays examined. These results reveal unique enzymatic characteristics of the Pols that provide new insights into their evolutionary divergence.
Collapse
Affiliation(s)
- Ruth Q. Jacobs
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Zachariah I. Carter
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Aaron L. Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A. Schneider
- Department of Biochemistry and Molecular Genetics, School of Medicine, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| |
Collapse
|
9
|
Jacobs RQ, Fuller KB, Cooper SL, Carter ZI, Laiho M, Lucius AL, Schneider DA. RNA Polymerase I Is Uniquely Vulnerable to the Small-Molecule Inhibitor BMH-21. Cancers (Basel) 2022; 14:5544. [PMID: 36428638 PMCID: PMC9688676 DOI: 10.3390/cancers14225544] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2022] [Revised: 11/09/2022] [Accepted: 11/09/2022] [Indexed: 11/16/2022] Open
Abstract
Cancer cells require robust ribosome biogenesis to maintain rapid cell growth during tumorigenesis. Because RNA polymerase I (Pol I) transcription of the ribosomal DNA (rDNA) is the first and rate-limiting step of ribosome biogenesis, it has emerged as a promising anti-cancer target. Over the last decade, novel cancer therapeutics targeting Pol I have progressed to clinical trials. BMH-21 is a first-in-class small molecule that inhibits Pol I transcription and represses cancer cell growth. Several recent studies have uncovered key mechanisms by which BMH-21 inhibits ribosome biosynthesis but the selectivity of BMH-21 for Pol I has not been directly measured. Here, we quantify the effects of BMH-21 on Pol I, RNA polymerase II (Pol II), and RNA polymerase III (Pol III) in vitro using purified components. We found that BMH-21 directly impairs nucleotide addition by Pol I, with no or modest effect on Pols II and III, respectively. Additionally, we found that BMH-21 does not affect the stability of any of the Pols' elongation complexes. These data demonstrate that BMH-21 directly exploits unique vulnerabilities of Pol I.
Collapse
Affiliation(s)
- Ruth Q. Jacobs
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Kaila B. Fuller
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - Stephanie L. Cooper
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | | | - Marikki Laiho
- Department of Radiation Oncology and Molecular Radiation Sciences and Sidney Kimmel Comprehensive Cancer Center, Johns Hopkins University School of Medicine, Baltimore, MD 21231, USA
| | - Aaron L. Lucius
- Department of Chemistry, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| | - David A. Schneider
- Department of Biochemistry and Molecular Genetics, University of Alabama at Birmingham, Birmingham, AL 35294, USA
| |
Collapse
|